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Old 3rd February 2004, 01:31 PM   #101
marcus66 is offline marcus66
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Hi all,

Drafance007: Thanks for posting pictures of your project! I just wanted to comment that it looks like the bias generator transistor T18 is mounted by itself on the PCB (?). This must be on the heatsink together with the output stage.
Also, PCB lines made using a marker pen can be a bit thin for the currents involved in a power amp. Perhaps you could reinforce the PSU lines with some copper wire?
An alternative way for making handmade PCBs is to cover the original blank copper surface in a layer of adhesive plastic, drill the holes, and then cut away the plastic with an x-acto knife where the copper is to be removed, leaving broad traces for high currents. This takes some time but gives good results, if the photographic method is not available.

Amp_man_1: Thanks for your comments. It is very interesting to hear if someone finds shortcomings in my design, in order that I can make improvements for future versions or new amp projects. However, I do not fully follow your points. For example, is a complementary output stage really a bad thing? It is not exactly an uncommon topology ?
The constant current source was shared in this design to keep the schematic simple. I have not had problems with this, but I may
very well consider other solutions for future projects.

Best wishes,

Marcus
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Old 3rd February 2004, 02:35 PM   #102
dimitri is offline dimitri  United States
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Dear Marcus,
The mentioned thoughts are only thoughts of the person with exaggerated self-appraisal and not shortcomings of your design. Forget them and move on.
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Old 3rd February 2004, 02:46 PM   #103
kASD is offline kASD
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Arrow Commentable Thoughts

Quote:
Originally posted by dimitri
Dear Marcus,
The mentioned thoughts are only thoughts of the person with exaggerated self-appraisal and not shortcomings of your design. Forget them and move on.

So Mr.Dimitri u think my thoughts are exaggerated self-appraisal type. OK thanx for these complements.

Friend Marcus I have 6 years of EXperience in Building Power amplifiers From 500W to 2000WRMS.
The thoughts I gave are based on my Expertise in fabricating Amplifiers. So take them in a way which is most suited to u.

I only comment when something is wrong in a circuit and
I am not that kind of a person who does self-appraises.

Regards
Ampman.
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Old 3rd February 2004, 05:54 PM   #104
subwo1 is offline subwo1  United States
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Also, complementary symmetry, especially using the emitter follower configuration, is a very good method due to less propagation delay. The shorter signal transit time makes the circuit more stable.
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Old 3rd February 2004, 07:48 PM   #105
Drafance007 is offline Drafance007
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well Marcus...as i allready wrote this is firs pcb i made and it passed very many test. The Bias transistor originaly was mounted on the heatsink but later i put it back on the pcb...couse i didn't want to lose it. You know how it is ehan working on several sides on several tables several amps You also may notes that there is no short-circuit protection...i put it away on prototype but i beleve that it works fine
The copper lines on the board are thick but they did survive averything ...even 2 ohm load.
Some day now i should get 300VA transformer and then i will have to made the original circuit with good semicondutors (mje340/350 instead bd139/140) etc etc.
only one question? I belive i can get the full power with less output devices than original (8 pcs)?
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Old 24th February 2004, 07:23 AM   #106
kvx is offline kvx  Philippines
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Quote:
So Mr.Dimitri u think my thoughts are exaggerated self-appraisal type. OK thanx for these complements.

Friend Marcus I have 6 years of EXperience in Building Power amplifiers From 500W to 2000WRMS.
The thoughts I gave are based on my Expertise in fabricating Amplifiers. So take them in a way which is most suited to u.

I only comment when something is wrong in a circuit and
I am not that kind of a person who does self-appraises.

Regards
Ampman.
It's not right to say that something is wrong with a design, in fact there is no such thing as an absolute correct desing, as if this is the case then we wouldn't need to make designs after all and all the amps in the world would be the same (or similar for amps with different power handling).

And as of M250, first it's not single-ended, the shared current source is for simplicity (and maybe economy), and there are actually pros and cons for any output stage, be it complementary or compound. M250 is a reliable amp, is excellent for constructors, and therefore not claiming professional standards.

By the way, i'm not used to posting into forums/thread.
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Old 28th March 2004, 01:26 PM   #107
sascica is offline sascica  Croatia
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where to find mje 15030 &15031 ???
i can't find them!!! they aren't in vrt-disk 2003 where are the most of tranzistors.... can we use some diferent ones???
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Old 28th March 2004, 04:48 PM   #108
JensRasmussen is offline JensRasmussen  Denmark
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Default Driver transistors

Hello,

Maybe you can get the 15032/15033 pair instead?

They schould work just fine as replacements since they have higher reatings.

\Jens
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Old 1st April 2004, 04:44 PM   #109
sascica is offline sascica  Croatia
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i can't find them tooo i asked on news groups and i'll try to find them outside croatia. the higest here are mj15024 & 25... thanks anyway
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Old 1st April 2004, 05:05 PM   #110
JDeV is offline JDeV  United Kingdom
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Quote:
Originally posted by sascica
where to find mje 15030 &15031 ???
i can't find them!!! they aren't in vrt-disk 2003 where are the most of tranzistors.... can we use some diferent ones???

You can order direct from On-Semi - samples,

http://www.onsemi.com/site/products/...E15030,00.html

up to 25 each and pay only US$20 shipping.
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